USB 3.0 - What's new in USB 3.0 and Compatibilty issues

USB 3.0 - What's new in USB 3.0 and Compatibilty issues

USB 3.0

When the USB (Universal Serial Bus) first came out, it was hailed as the solution for all personal computer connectivity. We’d finally be able to connect all our peripherals with one simple FAST connector, which would replace the multiple serial and parallel connections that had been in use since IBM came out with their first personal computer.


Of course, that idea lasted about as long as it took for computers to get faster. Considering that processor and buss speeds were still increasing rapidly at that time, maybe we were all a little short-sighted. It wasn’t long until this great connection we had was struggling to keep up. That led to the first upgrade (1.1) which was quickly replaced by USB 2.0 a mere four years after USB first came on the scene. USB 2.0 offered much faster transfer speeds, jumping from a mere 12 Mbit/s to 480 Mbit/s.


While USB 2.0 is excellent for many peripheral operations, it has always been a bit slow for data drives. Yet, USB thumb drives are one of the most popular applications of USB technology; an easily portable storage device, which is read/writable and has a large capacity. No wonder flash drives have pretty much totally replaced floppy drives, CDs and even DVDs for data transfer. They are even being used by software manufacturers to deliver their products; having taken a lot of that market from CDs and DVDs.


The challenge of using USB 2.0 with hard drives (either conventional rotational or SSDs) hasn’t prevented people from doing so. External hard drive sales that connect via USB are far higher than external hard drives ever were before the invention of USB. However, frustration has plagued external drive users, as they wait for their files to transfer.


This frustration was increased when compared to Apple’s FireWire connection, which always had much higher transfer speed than USB. In addition, the FireWire protocol allowed full-duplex communications, which USB 2.0 didn’t have. This increased the overall effectiveness of FireWire considerably.


USB 3.0 was released in November of 2008, in order to provide a new, faster data transfer rate of 5.0 Gbit/s. This put it at ten times faster than the previous 2.0, plus adding a lot of other capability. A version 3.1 was released in July of 2013, doubling the speed of 3.0 to 10 Gbit/s. This will bring the USB standard up to par in transfer speed, in comparison to Thunderbolt (the latest version of FireWire).


What’s Different About USB 3.0?

The major difference between USB 3.0 and USB 2.0 is the speed. At more than tenfold increase in transfer speed, USB 3.0 outperforms FireWire 800 and is just about on par with Thunderbolt. This increase in speed is especially noticed when using an external hard drive or SSD (solid-state drive).


To gain this increase in transfer speed, a number of things have been done differently on the USB 3.0 connection. Five additional contacts were added to the four that are on the original USB specification. While the USB 2.0 and 3.0 connections look almost identical and will physically fit in each other’s receptacles, the additional contacts in the USB 3.0 connector have a lot to do with the added speed that the connector provides. USB 3.0 connectors are identifiable by their blue plastic insert, whereas the USB 2.0 connectors have a black plastic insert.


These additional contacts are providing two SuperSpeed transmission pairs, labeled as “SuperSpeed transmission” and “SuperSpeed receiver.” This gives the USB 3.0 full-duplex capability. That means that in full-duplex mode, actual data transmission in both directions is 10 Gbit/s for USB 3.0.



The USB 3.0 connection still has the half-duplex connection that was included in the original USB specification, allowing devices with USB 3.0 connectors to be plugged into USB 2.0 sockets and communicate through them. Obviously, the device will be limited by the transfer speed of the USB 2.0 protocol; but even then, USB 3.0 drives will transfer graphics and video four to six times faster than a USB 2.0 device will.


USB 3.0 is both backwards and forwards compatible with USB 2.0. That means that USB 3.0 devices can be connected to USB 2.0 sockets and USB 2.0 devices can be connected to USB 3.0 sockets. The design of the USB 3.0 connector leaves the same contacts in the same places as used for USB 2.0, while adding those additional five contacts.



There is an exception to this. The USB 3.0 mini connector is not compatible with the USB 2.0 mini. To add the additional contacts, the USB 3.0 mini connector is considerably wider than the USB 2.0 mini connector, adding the new contacts to the side of the original group.  


Rich Murphy